The present disclosure relates to a sheet feeder capable of feeding a sheet to a predetermined position, and an image-forming apparatus having the sheet feeder.
An image-forming apparatus such as a printer, a copier, or a facsimile typically includes an image-forming section for carrying out an image-forming process to a sheet, a sheet feeder for storing sheets and for feeding the sheets to the image-forming section, and a sheet path along which the sheet is carried through the image-forming section. The sheet feeder and the sheet path include a plurality of rollers for carrying sheets. For example, the sheet feeder includes a payout roller that pays out a sheet stored in a tray, a feed roller that delivers the sheet that has been paid out to the sheet path, and a separation roller pressure-contacted to the feed roller and preventing overlapping of sheets.
While the rollers are demanded to rotate in an intended manner, an expected rotating speed may often not be obtained due to continued use. For example, the separation roller can be worn due to continued use, and may not rotate following the feed roller successfully. In this case, the separation roller is required to be replaced. In order to monitor time for replacement, a sensor for detecting a rotating speed of the separation roller is provided for the sheet feeder in some cases. As a sensor for detecting a rotating speed of a rotating body, for example, an encoded-type using a reflector with a slit is known.